Electric drill-motor.



No. 794.398. PATENTED JULY 11, 1905.

F.E.DRAKE. I

ELECTRIC DRILL MOTOR. APPLICATION FILED SEPT. 30. 1904.

witness Svwewtoz 351 @lttomac I /24 Q, J 1d UNITED STATES 'Patented July 11, 1905.

PATENT OFFICE.

ELECTRIC DRILL-MOTOR.

SPECIFICATION forming part of Letters Patent No. 794,398, dated July 11, 1905.

' Application filed September 30, 1904. Serial No. 226,622.

To aZZ whom it may concern:

Be it known that I, FRANCIS E. DRAKE, a citizen of the United States, residing at the city of St. Louis, State of Missouri, have invented certain new and useful Improvements in Electric Drill-Motors, of which the following is afull, clear, and exact specification.

My invention relates to electric motors for drills, and is particularly applicable to that class of reciprocating motors known as electric percussion drills. The advantage of electricity as a motive power for this class of work has long been recognized, and many efforts have been made to introduce electric drills which would stand the heavy work imposed upon them. Among the mostsuccessful machines have been those of the solenoidplunger type, which have the important advantage of simplicity in construction which is particularly necessary in machines of this character. One of the most desirable constructions comprises two solenoids which are alternately excited to give a reciprocating motion to their cores and the tool carried thereby. In practice, however, it has been found that machines of this type, owing to the necessity of keeping the weight small, and therefore a limited amount of material, become greatly overheated under continued service, which ca uses the rapid deterioration of the parts and reduces their ei'ficiency.

The objectof my invention is to overcome the excessive heating in machines of this class. and in carrying out my invention I provide a means for ventilating the machines under a forced draft, and sointroduce the ventilating means that it becomes a part of the machine itself. I further provide means whereby the ventilating means may be operative while the drill is at rest or in operation, or at the will of the operator.

My invention will be understood by reference to the followingdescription in connection with the accompanying drawings.

Figure 1 is a longitudinal sectional View of a drill embodying my improvement. Fig. 2 is a section on line 2 2 of Fig. 1, and Fig. 3 is a diagram of the electrical apparatus and connections.

Referring to Fig. 1, 1 indicates an outer cylindrical shell forming the main casing of the machine and carrying the end heads 2 3. Within the'shell l are located the two exciting-coils 4t 5, suitably insulated and inclosed by the inner and outer metal coverings 6 7 and end heads 8. A cylindrical space 9 is formed between the coils and the outer casing 1. Within the coils is located the plunger, which is made up of a steel part 10. carrying the tool 11, a rifled steel portion 12, and an intermediate connecting portion 13 of brass.

The rifled part 12 passes through a guide 1 1 and engages one end of acushioning-spring 15, suitably inclosed and supported by a casing 16, between which and the outer casing there is also formed a cylindrical space 9. At one end of the casing 16 is located a head 17, and between this head and the head 3 is located an electric fan-motor. The shaft of the armature 18 is journaled in the heads 3 17 and carries the fanblades 19. The poles 20 of the electric motor are shown. as extending from the head 3 in the present instance, and the brushes may also be carried by supports extending from the head 3. In the heads 2, 17, and 3 are provided a so ries of circumferentially arranged holes 21, which in the heads 2 and 17 communicate with the space 9 and in the head 3 with the chamber in which the motor is located. Additional holes may be provided in the head 3, such as at 22, and also in the casing 1 back of the 'fan-blades 19, as shown at 23. Current may be led into the coils 1 5 by any suitable connections, one of the terminals being indicated at 2A. The machineis slidably mounted upon the frame 25, its position beingcontrolled by a screw 26, which engages said frame and also passes through a lug 27, formed on the head 3. Thus when the screw is turned by its handle 28 the machine may be moved as a whole forward or backward. The frame is mounted upon the dovetail 29 and may be adjusted sidewise in any position thereon and secured in place by the clamp 30 and screw 31. r The electrical connections are diagrammatically shown in Fig. 3, in which 4 5 represent the plunger-coils, 10, 13, and 12 the plunger, and 11 the tool. The fan-motor armature is indicated at 18 and its shunt-wound poles at 20. Although various arrangements of circuits may be used for operating the drill, the method shown is preferable. As illustrated, the direct-current-supply mains 32 33 have connected theretoa shunt-wound electric motor 34, which drives the generator 35 either directly, as indicated, or through suitable gearing. This generator has its field 36 separately excited and connected to the supplymains 32 33. Its armature comprises a single coil 37 wound in one plane. One end of the coil is connected to the collector-ring 38 and the other end to the half collectorring 39. A brush 4L0 bears upon the ring 38 and is connected at 41 to both coils t and 5. The diametrically opposite brushes 42 43 contact alternately with the half-ring 39 and are connected, respectively, to the outer ends of thc coils 4 5. An independent circuit 44 leads from the mains 32 33 to the fan-motor armature and fields.

In the operation of the apparatus the current generated in coil 37 will be an alternating one, and by means of the slip-rings and three brushes the current generated in one direction in coil 37 will be delivered to coil 4 and that generated in the opposite direction will be delivered to coil The coils et 5 will therefore be alternately excited and attract their cores 1O 12, givinga reciprocating movement to the tool 11. Also, whether the drill is in operation or not, the fan-motor by reason of its independent circuit may be continuouslyoperated and maybe stopped or started at the will of the operator by opening or closing the switch 47. The forced ventilation may therefore continue during intervals when the drill is not in operation. This is an important consideration, as in work of this character the drill is frequently stopped, and these periods of rest may be taken advantage of by the continued operation of the fan, resulting in a reduced weight of the parts required over the weights whichwould otherwise be necessary. The fan acts to draw cool air into the chamber through the holes 21, 22, and 23 and drives the same through the holes 21 in head 17into the open space 9. The air in its passage through this space comes in contact with the exterior of the coils t 5 and other parts of the machine, and the heated air passes out through the holes 21 in the head 2. The air may also pass through the perforations 45 in thehead 17 into the casing inclosing the cushioning-spring I5 and out through perforations 46 in this casing. The reci 'n'ocation of the plunger will also aid in -ausinga rapid circulation of air through the machine.

While I have shown and described a particular form of construction and arrangement of circuits, it is understood that I do not confine myself to the exact construction shown and that wide departures may be made in the detail construction without departing from the spirit of the invention or scope of the claims. For example, various arrangements of exciting-coils and plunger may be used and the form and arrangements of the air-passages may be materially changed. Also other forms of generating means may be used and an alternating as well as direct current supply.

Having thus described my invention, I declare that what I claim as new, and desire to secure by Letters Patent, is-

1. The combination of an electric drill hav' ing an outer casing and passages for the circulation of air, an electric fan-motor within said casing for forcing air through said passages, a supply circuit for operating said drill, and an independent suymly-circuit for operating said fan-motor.

2. In an electric motor of the reciprocating type, the combination of a plunger, excitingcoils for reciprocating said plunger, a supplycircuit for said coils, an outside casing forming an air-passage between said coils and said casing, an electric fan-motor for forcing air through said passages, and an indepemlent supply'circuit for said fan-motor.

3. In an electric motor of thereciprocating type, the combination of a plunger, excitingcoils for reciprocating said plunger, an outer casing forming an air-rmssage between said coils and said casing, ahead at one end of said casing and a second head within said casing forming a chamber, said heads having openings, and an electric fan-motor in said chamber.

4. In an electric motor of the reciprocating type, the combination of a plunger, excitingcoils for reciprocating said plunger, an outer casing forming an air-passage between said coils and said casing, a head having openings at one end of said casing forming a chamber, an electric fan-motor supported by said head and located in said chamber.

Inan electric motor of the reciprocating type, the combination of a plunger, exciting coils for reciprocatingsaid plunger, an outer casing forming an air-passage between said coils and said casing, a head having openings at one end of said casing, a second head having openings communicating with the space in which said plunger reci1n'o(.'atcs, and an electric motor located between said heads.

In testimony whereof I al'lix my sigimture in presence of two witnesses.

FRANCIS E. DRAKE. 

